Tuesday, August 19, 2014

Summary: The bias on the PMT was turned to its
maximum safe value of 1500 V for maximum gain.
There is a bit of a voltage drop in the PMT base between supply voltage
and the anode voltage, so at 1500 V supply voltage, we’re still not running at
the maximum rated cathode to anode voltage of 1500 V. Using peaks from several sources, a channel
vs. energy graph was constructed.
Although some of the peaks have small counts and need to be measured
more accurately, the linearity looks good with a resolution of about 188 V per
channel and a maximum detectable energy of about 203 keV.

If you're new to the experiment, scroll to the bottom for background information.

Data and Channel vs. Energy Mapping

Bias

1500 V

Gate Window

0.5 uS

Threshold

1.5mV

Attenuation

0 dB

Data set

HBC_00011

Source

Am 241 Taped to window

Start Time

~ 11:17 AM

Stop Time

~~ 1:30 PM

Date

2014_08_19

x-y scope V/div

1, 0.5

Shielded?

Yes

Tube

Harshaw B-

Spectrum Data

Bias

1500 V

Gate Window

0.5 uS

Threshold

1.5mV

Attenuation

0 dB

Data set

HBC_00012

Source

Cd 109 Taped to window

Start Time

2:18 PM

Stop Time

2:50 PM

Date

2014_08_19

x-y scope V/div

1, 0.5

Shielded?

Yes

Tube

Harshaw B-

Bias

1500 V

Gate Window

0.5 uS

Threshold

1.5mV

Attenuation

0 dB

Data set

HBC_00013

Source

Background

Start Time

2:56 PM

Stop Time

3:37 PM

Date

2014_08_19

x-y scope V/div

1, 0.5

Shielded?

Yes

Tube

Harshaw B-

Bias

1500 V

Gate Window

0.5 uS

Threshold

1.5mV

Attenuation

0 dB

Data set

HBC_00014

Source

Cs 137 Taped to window

Start Time

3:35 PM

Stop Time

3:59 PM

Date

2014_08_19

x-y scope V/div

1, 0.5

Shielded?

Yes

Tube

Harshaw B-

This run needs to be much longer to get more reliable
statistics. The run today was a short
one to get a ballpark picture of the detector’s channel vs. energy behavior

Channel Mapping

Using the peaks location from the three sources listed
above, Am 241, Cd 109, and Cs 137, the response of the detector with respect to
energy was mapped out.

The data for the peak locations is shown in the table below

Source

Peak Channel

Energy eV

Cd109

55

22100

am241

86

26344

Cs 127

104

32000

Am241

262

59541

Cd109

406

88000

1023

203390.39

The last row is a calculation using the least squares
regression fit parameters to determine the maximum energy that can be detected.

The peak energies vs. channel are shown in the following
graph.

Background

Hirsch's theory of hole superconductivity proposes a new
BCS-compatible model of Cooper pair formation when superconducting materials
phase transition from their normal to their superconducting state[1]. One
of the experimentally verifiable predictions of his theory is that when a
superconductor rapidly transitions, (quenches), back to its normal state, it
will emit x-rays, (colloquially referred to here as H-rays because it's
Hirsch's theory).

A superconductor can be rapidly transitioned back to its normal state by
placing it in a strong magnetic field.
My experiment will look for H-rays emitted by both a Pb and a YBCO superconductor
when it is quenched by a strong magnetic field.

This series of articles chronicles both the experimental lab
work and the theory work that’s going into completing the experiment.

The lab book entries in this series detail the preparation and execution of
this experiment… mostly. I also have a
few theory projects involving special relativity and quantum field theory. Occasionally, they appear in these pages.